RF Resonance Measurement of Electron Depletion in a Dusty Plasma

Active plasma resonance spectroscopy (APRS) is a class of plasma diagnostics which utilizes plasma resonances at or near the electron plasma frequency, ω_pe. Adding dust to a plasma affects ω_pe as dust particles become charged. This dust charge is typically highly negative because of the higher mobility of electrons as compared to ions. The negative dust charging leads to a reduction in the electron density in the surrounding plasma and a reduction in ω_pe related to this electron density depletion. APRS diagnostics are useful for measuring this phenomenon. Such a measurement is difficult with many common plasma diagnostic techniques because many of these techniques are undesirable for use with dusty plasmas. For example, a Langmuir probe can perturb the dust, or it can become unreliable due to dust contamination. In this poster, we present experimental results from APRS measurements showing ω_pe reduction in a plasma due to the injection of dust. We also present preliminary results from similar experiments conducted in the presence of a magnetic field.